Evaluate my Camshaft Position Deviation Readings

I have read about camshaft position deviation readings, borrowed a friend's Autel MaxiDAS DS708 and took some measurements. What I have found is that initially you get a higher deviation reading on bank 1 when cold, then it comes down as the engine warms up. I assume that this is due to parts expanding and taking up clearance / "slack" in the chain. I know there is no slack, but it does not have to adjust for it as much. The warmer the engine, the smaller the deviation. Spec is with +/- 6.0 degrees, I am above that. My car presently has 37K miles. Would you do anything more than just continue to monitor it periodically? The "actual" angle for camshaft was normal and would change over around 2,000 RPM or so. A few screen shots: Now with RPM showing: Actual angles don't change with engine RPM, except for the change over, they are constant within their range. If you are interested in the tool I used, I am considering getting one of these used or new vs. a Durametic.

Very cool! I must agree with the idea of some sort of "settling down" after a nice cold start that we would expect on a motor with how many moving parts? I am shooting in the dark with this but since your numbers are very close I would say that most people would leave it alone and just monitor it. Your motor is clean as a whistle (I have seen her) and unless you have seen anthing in the oil you are probably doing ok. If you eventualy go down the road to rebuild your motor some day budget for the nice LN Engineering's Billet Aluminum Tensioner Paddles... -joe

The cam deviation values will be a little different every time you start the engine but as long as they hold steady and don't change with rpm, they are OK as long as the values are in spec. If they fluctuate with rpm, that means something is wobbling e.g., IMSB. Now the -7 degree out of spec (+/- 6 degrees) means the cam pads have worn a bit (assuming your engine is stock and never has been opened). With 7 degrees out (measured at the crankshaft), that's 3.5 degrees out on the cam and you should be able to see that if you remove the cam plugs. Probably not worth opening the cam cover yet.

Looks like a 5 chain engine with +/- 40K miles, thats lived on M1 with factory wear pads. You are 2/3 the way to setting an out of range CEL with these values.

Thanks Jake....changed to Joe Gibbs oil last oil change and will continue to run it and trend the camshaft readings. Pretty cool to do some predictive monitoring with that tool. It is possible to change the pads without dismantling the motor?

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Interesting, so less than 40k motor has 2/3 the way of setting out of range CEL with the factory wear pads? If that's the case shouldn't most people see this CEL on motors with over 100k with their original wear pads that's been on M1 all it's life?

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Driving style, oil services and etc have a tremendous amount to do with this. Driving the car at low speeds is the biggest contributor to this, along with extended oil services. The lower the speed the engine sees, the more load these units see, due to the position of the actuator that they operate with. We've only had 6, 5 chain engines pass pre- evaluation for preventative packages in the last year because of this particular gripe. Its to the point now that I either send a prospective owner a scan tool to check these before they ship the car to us, or we have them get the ECU interrogation done locally before they ship the car. No use landing a car here from far away that we will down in the first 30 seconds of the pre- eval. Its a little late to add the DT40 oil now, as the wear pads are already through the dermis, and epidermis layers, and into the softer material thats deeper within the wear pad. The wear progresses faster, as it digs deeper into the wear pad. Replacement pads have a much stronger, and harder epidermis layer, and resist wear greatly. This is especially so when better oils and surface coatings are applied to them.

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Thanks for the clarification. Considering my car has over 125k on original motor and original IMS using M1 all it's life, I guess it's doing pretty good then. Just to clarify given Paul's case, if his car was at your place, would it fail prequal at this point?

alpine: Do you know what your readings are? Is your car a MK1 or 2?

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Yes. It would fail immediately. I'm not going to touch an engine that will set a valve train related fault anytime in the near future. These deviations also can create issues where cam timing jumps during a procedure. My max allowable is 5 degrees total deviation, but even with that I have a serious chat with the owner.

I guess I'll have to figure out how easy or how hard it would be to replace the pad on the car.

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Common advice is to drop the engine and I can totally see why. You need to remove the cam covers and the cams then re-time and engine afterwards. Will be hell working in situ.

I have done it in the car.. Can be done, but its a bitch and you can't work the assembly nearly as well.

Winter project Paul? I'm up for helping out if I get a kitchen pass!

Thanks for the info Jake! I need to check mine now...

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Mk1. Don't know and don't care. Life's too short. If it breaks after I wail on it some more, I'll repair it or replace it. This is just another car for me. A lot of people think they "own" their cars but they really don't.

I've never felt that way about any Porsche I've owned. I do believe that a great deal of 996 owners feel this way, which to me, is sad.

Thank you Paul! Now we have something else to worry about! Thanks!

Let me know if you decide to tackle this Paul, I will lend a hand.

Great thread. Any updates on your values? Ended up here from the link you posted to it obviously.

what year is your 996. the + - 6% is clearly stated for the variocam engines but i have not seen any tolerances for the variocam plus system. they very different. it looks like the actual values are being controlled properly.

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i suspect the curved chain rail on the left of the attachment is worn causing the difference you are seeing. The crank and cams turn clockwise and the tension side, where there is more force, is riding on the curved rail on bank 1 and straight rail on bank 2. Some wear on that rail would cause the minus deviation. changing that rail would probably bring down the deviation. don't know if it can be changed with engine installed.

just noticed that you have a 99 so my posts are irrelevant. sorry.

I have a 99 C2 with its engine replaced in 2005 by the dealer. I took it to an indy mechanic to check the cam deviation and got a 0.0 on both banks, they were puzzled and told me to drive it for a few weeks. So I did and took it in again this morning. Again the cam deviation was reading 0.0 on both banks, even when we revved up to 4Krpm. Anyone else have seen this problem? Perhaps there is something wrong with my DME?

To OP - I had simillar readings to yours on my Ex 2001 . Bank one was around 6.5 and bank two around 3.5. I replaced the pads and got readings pretty close to 1. Word of advice if you'll be tackling this yourself - see if your manifold bolts on bank two are still removable. Chances are they are seized , then it's a P.I.T.A I'll be doing my pads on this new to me 2001 this winter, first thing I did when I got the car, was to remove all manifold bolts just to see if they are seized or not (I got lucky, they all came out) and put them back with antiseize

Hi Paul, Thanks for lending the Durametric. I tested my cam deviations with a cold engine and then had to let the engine warm up idling (not recommended, but I couldn't drive it to warm it up). So, my cam deviations (position 1 and 2 respectively) started cold at -2 and -4. Then, during warmup, they switched to -3 and -3 for awhile. I also noticed that oil temps are lagging my cooling temps by -15-20C. Water was at 94 and oil is at 74. As Oil and water started to slowly creep up (82C/95C) cam deviations switched to -2 and -3 and then after a few more mins, went to -1 and -3. Another check with oil/water at 85/97C, deviations are -0 and -3 Another check oil/water at 87/100C and I'm at -0 and -3 I let my car's water temp get as hot as can be, this whole time, the oil temps didn't go above 90C and cam deviations didn't change from -0 and -3. My car has only 51,500 miles